Junction pickup device



Sept. 24, 1957 c u 2,807,666

JUNCTION PICKUP DEVIC'E Filed Feb. 28, 1956 2s 24 1 /ls l ll I6 INVENTOR Lloyd R Cramp 2,807,666 Patented Sept. 24, .1957

ilnited rates Patent @zfiice Z,8tl7,666

JUNtITlQN lllCKlUl? DEVECE Lloyd R. Cramp, Silver Spring, Md. Application February 23, 1956, Serial No. 563,329

1 Chain]. (Cl. 17-1) This application is a continuation-in-part, of an application filed by Lloyd R. Crump, Serial No. 441,716 on Junction Pickup Device.

This invention relates to sound detecting or Vibration detecting systems, and particularly to a sound detecting system in which a transducer responsive to sound or to vibrations is connected by a single wire to a listening post at a remote point.

It is an important object of this invention to provide means whereby a load device at a listening post and carrying current over a single wire to a remote sound responsive device will have the current in the load device modulated by the remote sound responsive device and so that sound, or other vibrations, received by the remote sound responsive device will actuate appropriate devices connected to the load device.

It is an object of this invention to dispose a transducer and a transistor in a metallic shield, and responsive to sound, and to connect the single output lead of this device to a single wire leading to a remote listening post, and to modulate a direct current flowing through a load device at the listening post so that a listener may hear or otherwise detect the sound picked up by the transducer and transistor.

It is an object of this invention to provide an arrangement of a transistor and a transducer with sufiicient electrical output in response to sound waves to modulate a direct current flowing in a single wire and connecting the transistor to a remote listening post and without necessitating the use of pre-amplifier means in the single wire.

It is an object of this invention to provide novel means comprising a transducer and a transistor placed in a shield and arranged responsive to sound waves in the vicinity of the shield, or arranged responsive to vibrations actuating said transducer, and with the transistor connected to a remote listening post through a single wire which carries current from a battery to modulate the current in the wire so that the sound waves or vibrations picked up by the transducer may be heard or otherwise detected at the listening post.

Other and further objects of this invention will appear in the description of the invention.

In the drawings:

Figure 1 is a diagrammatic showing of the circuits connecting the assembly of the transistor and the transducer with a remote listening post.

Figure 2 is a circuit embodying the invention using a carbon mike for the pickup element.

Figure 3 is a wiring diagram showing the assembly of the transistor and transducer in various uses.

In the figure a transducer is connected by wires 11 and 12 to the emitter terminal 13 and to the base terminal 14, respectively, of a transistor 15. The transducer 10 may be of any suitable type, and for simplicity it is shown as a reuluctance type with the movable element 16, engaging the cone 17 of a closure member 18 of a metallic housing 19, and is arranged capable of vibrating when exposed to sound waves.

The metallic housing is suggested when the device is to be submerged in water in military uses, but the housing may be of any suitable material and lined with ametallic shield to prevent spurious pick up of unwanted electrical charges. I I

The transistor shown is of the p-n-p type, but the in vention is not limited to this specific type. I I

A wire 20 is connected to the emitter wirelL-and is connected to the metallic housing 19 so that we have a grounded emitter. A wire 21, extends from the collector terminal 22. and out through an appropriately sealed opening in the metal housing. I I I I I The wire 21 is connected to a metallically shielded wire 24, and this shielded wire may extend for several miles to a listening post where it is connected to a resistor 25,

and then to the negative pole of a battery 26, which has its positive pole grounded. Well known means are con: nected to the resistor 25 to be actuated by the voltage drop in the resistor, and such means are indicated generally by the numerals 28. The voltage of the battery will depend upon how long the line 24 is and its ohmic resistance, and on the proper operating current of the transistor, and a mil'liammeter 29 may be connected in the line to guide the operating personnel in determining the proper battery voltage.

It is obvious that a twin lead may be used instead of the single wire and its ground connections, but the single wire offers many practical advantages in cost and handling.

The metallic housing 19 is connected to ground, as indicated at 40, and it may be connected to the metallic shielding braid around the wire 24.

The transistor may be thought of as an impedance matching device for it is the transistor and not the transducer that is connected to the line, and its impedance is more of a match for the line than that of the transducer.

It will be understood, of course, that other means than the resistor 25 can be used to indicate the modulation of the current in the wire 24, and that the resistor 25 is used for illustration purposes because of its simplicity.

The pick up device lends itself particularly well to sound ranging in military uses. As shown in Figure 3, three pick-up devices are positioned as at the corners of a triangle and the operating personnel may switch to any one of the connecting wires by a switch 29.

The connecting wires from the listening post to the pick-ups may have a shielding braid of Woven metal, but in many instances the connecting wires may be of the usual run of insulated wire for the output of the transistor is well above the noise in the wire and well above the spurious electrical charges in the wire so that adequate performance of the arrangement is possible.

As indicated at 30, the metallic housing 19 may be substantially insulated from ground, and it is connected to ground 33 by a wire 31 through a relay 32, which may be connected to an explosive mine, indicated at 34. A battery 35, of an adequate voltage to operate the relay 32, may be connected to the line 36 through a switch 37, so that when the switch 37 is in its normal position connecting the listening post to the housing 19 and the movement of enemy troops or vehicles is heard going over a bridge, the switch 37 may be moved to connect the battery 35 to operate the relay 32 and the mine 34, to blow up the bridge.

The relay 32, or its equivalent, will ususally be in the mine but it is shown as external to the mine for ease in illustration.

The pick-up 19 may be momentarily by-passed by the current from the battery 35 through a gas diode responsive to the added voltage so that a path is available for the kick from the battery 35, but yet will not materially affect the performance of the pick-up as it operates under its normal low voltage from the battery 26, the diode ofiering a ready path for the increased current needed to operate the relay 32.

The pick-up device of this invention is especially adapted for under-water use in detecting the presence of enemy vessels, and the fact that only one wire is necessary to connect it to an observing station gives it very outstanding practical value over prior art pick-ups calling for multicore cables connecting the pick-up to the observing station.

The shielding housing 19 may be connected to a conventional sound producing device, such as a phonograph, and the output of the sound producing device will modulate the current in long single wire connected to a loud speaker at a remote point. In this example, the impedance of the loud speaker does not have to be matched to-the impedance of the transducer which, in some instances, is very much higher than that of the loud speaker.

An additional transistor may be placed in the metallic housing 19 to amplify the modulating effect of the transistors on the current in the single wire.

The usual care is taken to mount the transistor and the transducer in themetallic shell 19 to avoid unwanted movement, of these elements, and to properly insulate them from unwanted contact with the metal of the housing.

Figure 2 ,is a circuit embodying the invention using a carbon mike for the pickup element. A carbon mike does not generate its own voltage. Therefore, voltage 4 must be supplied to the mike. This is accomplished by a condenser across the mike and charging said condenser from the remote listening post.

I claim:

A sound detecting system comprising a housing, a transistor and a transducer within said housing, circuit means connecting said transducer with said transistor, means connecting said transistor in circuit with said housing, a sound actuated device at a point remote from said housing, a current actuated device operably connected with a mine or the like, means connecting said housing to ground through said current actuated device, a first battery having one pole connected to ground and having its other pole connected to said transistor through said remote sound actuated device and through a single wire, a second battery connectable to said wire to actuate said current actuated device and having one pole connected to ground and the other pole connectable to said Wire, and means in circuit with said first battery to disconnect said first battery when said second battery is connected to said wire.

Bell Mar. 7, 1876 Stutz Dec. 25, 1956 

